heart rate changes while getting asleep / waking up

Hi! I've got a confirmed POTs diagnosis through tilt table testing (66bpm increase after 10 minutes head up, 90bmp to 156bpm, that is. The thing is that I experience something that isnt' described in any text about POTS or other disautonomy disorders. When I lay in bed in order to sleep and my heart rate becomes progressively slower, which is natural. The thing is that if my relaxation is stopped, say, for example, by somebody calling my name or the door bell ringing, my heart rate spikes immediately to what I think is the bpm I experience when changing from supine to standing position. But that's not all, I also get dizziness and lightheadness, along with a generalised weakness. In sum, I experience the same symptoms that I'd had if I suddenly got up from a lying down position, only that not due to a change in position, but due to a change from a pre-sleep state to one in which in more alert. This thing can happen many times while I'm trying to sleep, if for example my child is demands my attention from time to time while I try to get asleep, and the more times this heart rate spikes occur, the worse I feel. I must add that these spikes also make my POTS symptoms worse once I'm awake having already slept. The question is, of course, does anybody have this symptoms, along with POTS or not? any insight on which condition could this symptoms fit? Thank you!

do not know if this is helpful but it sounds like the startle effect to do with the fight or flight response

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it might well be, however, this symptom started along with the symptoms from POTS, they're clearly related, maybe whatever physiological disturbance that is causing my POTS does also affect this "startle effect" phenomena?

It doesn't feel like a startle response. Almost the opposite. It feels like really drifting off to sleep changes my blood pressure and heart rate. I just took shower and my heart rate went from 50 to 40 to 199 to 64 and back up. I don't know whether it is standing up, hot water or having my hands above my head while washing my hair. Often, I don't feel any different, though today I felt dizzy.

I should also add one thing: there is one thing that makes the symptoms banish completely for a short period, the emotion of RAGE. The few times I felt genuinely enraged and prepared to literally fight with another person are also the very few times I felt healthy in the last 20 years, all the pots symptoms simply disappeared while the rage lasted. Does this sound familiar to anybody?